v0 + shadcn/ui — Empty DataTable on 3G (No Loading States)

// ============================================
// Production Data Table — v0 scaffold + engineering layer
// ============================================

'use client'

import { useState } from 'react'
import { useDebouncedCallback } from 'use-debounce'
import {
  ColumnDef,
  flexRender,
  getCoreRowModel,
  getSortedRowModel,
  getFilteredRowModel,
  SortingState,
  ColumnFiltersState,
  useReactTable,
} from '@tanstack/react-table'
import {
  Table,
  TableBody,
  TableCell,
  TableHead,
  TableHeader,
  TableRow,
} from '@/components/ui/table'
import { Input } from '@/components/ui/input'
import { Button } from '@/components/ui/button'
import { Skeleton } from '@/components/ui/skeleton'
import { Card, CardContent } from '@/components/ui/card'
import { ArrowUpDown, Search, RefreshCw } from 'lucide-react'
import { cn } from '@/lib/utils'

interface Invoice {
  id: string
  customer: string
  amount: number
  status: 'paid' | 'pending' | 'overdue'
  date: string
}

const columns: ColumnDef<Invoice>[] = [
  {
    accessorKey: 'customer',
    header: ({ column }) => (
      <Button
        variant="ghost"
        onClick={() => column.toggleSorting(column.getIsSorted() === 'asc')}
      >
        Customer
        <ArrowUpDown className="ml-2 h-4 w-4" />
      </Button>
    ),
    cell: ({ row }) => row.getValue('customer'),
  },
  {
    accessorKey: 'amount',
    header: 'Amount',
    cell: ({ row }) => {
      const amount = parseFloat(row.getValue('amount'))
      return new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' }).format(amount)
    },
  },
  {
    accessorKey: 'status',
    header: 'Status',
    cell: ({ row }) => {
      const status = row.getValue('status') as string
      return (
        <span className={cn('inline-flex items-center rounded-full px-2.5 py-0.5 text-xs font-medium',
          status === 'paid' && 'bg-emerald-100 text-emerald-800 dark:bg-emerald-900 dark:text-emerald-200',
          status === 'pending' && 'bg-yellow-100 text-yellow-800 dark:bg-yellow-900 dark:text-yellow-200',
          status === 'overdue' && 'bg-red-100 text-red-800 dark:bg-red-900 dark:text-red-200'
        )}>
          {status}
        </span>
      )
    },
  },
  { accessorKey: 'date', header: 'Date' }
]

function TableSkeleton() {
  return (
    <div className="rounded-md border">
      <Table>
        <TableHeader>
          <TableRow>
            <TableHead>Customer</TableHead>
            <TableHead>Amount</TableHead>
            <TableHead>Status</TableHead>
            <TableHead>Date</TableHead>
          </TableRow>
        </TableHeader>
        <TableBody>
          {Array.from({ length: 5 }).map((_, i) => (
            <TableRow key={i}>
              <TableCell><Skeleton className="h-4 w-[180px]" /></TableCell>
              <TableCell><Skeleton className="h-4 w-20" /></TableCell>
              <TableCell><Skeleton className="h-4 w-16" /></TableCell>
              <TableCell><Skeleton className="h-4 w-24" /></TableCell>
            </TableRow>
          ))}
        </TableBody>
      </Table>
    </div>
  )
}

function EmptyState({ onReset }: { onReset: () => void }) {
  return (
    <Card className="flex flex-col items-center justify-center py-12">
      <CardContent className="text-center">
        <p className="text-muted-foreground">No invoices found</p>
        <Button variant="outline" className="mt-4" onClick={onReset}>Clear filters</Button>
      </CardContent>
    </Card>
  )
}

function ErrorState({ onRetry }: { onRetry: () => void }) {
  return (
    <Card className="flex flex-col items-center justify-center py-12">
      <CardContent className="text-center">
        <p className="text-destructive">Failed to load invoices</p>
        <Button variant="outline" className="mt-4" onClick={onRetry}>
          <RefreshCw className="mr-2 h-4 w-4" />Retry
        </Button>
      </CardContent>
    </Card>
  )
}

interface DataTableProps {
  data: Invoice[]
  isLoading: boolean
  isError: boolean
  onRetry: () => void
}

export function DataTable({ data, isLoading, isError, onRetry }: DataTableProps) {
  const [sorting, setSorting] = useState<SortingState>([])
  const [columnFilters, setColumnFilters] = useState<ColumnFiltersState>([])

  const debouncedFilter = useDebouncedCallback((value: string) => {
    table.getColumn('customer')?.setFilterValue(value)
  }, 300)

  const table = useReactTable({
    data,
    columns,
    getCoreRowModel: getCoreRowModel(),
    getSortedRowModel: getSortedRowModel(),
    getFilteredRowModel: getFilteredRowModel(),
    onSortingChange: setSorting,
    onColumnFiltersChange: setColumnFilters,
    state: { sorting, columnFilters },
  })

  if (isLoading) return <TableSkeleton />
  if (isError) return <ErrorState onRetry={onRetry} />
  if (data.length === 0) return <EmptyState onReset={() => setColumnFilters([])} />

  return (
    <div className="space-y-4">
      <div className="flex items-center gap-2">
        <Search className="h-4 w-4 text-muted-foreground" />
        <Input
          placeholder="Filter by customer..."
          onChange={(e) => debouncedFilter(e.target.value)}
          className="max-w-sm"
        />
      </div>

      <div className="rounded-md border">
        <Table>
          <TableHeader>
            {table.getHeaderGroups().map((headerGroup) => (
              <TableRow key={headerGroup.id}>
                {headerGroup.headers.map((header) => (
                  <TableHead
                    key={header.id}
                    aria-sort={header.column.getIsSorted() === 'asc' ? 'ascending' : header.column.getIsSorted() === 'desc' ? 'descending' : 'none'}
                  >
                    {flexRender(header.column.columnDef.header, header.getContext())}
                  </TableHead>
                ))}
              </TableRow>
            ))}
          </TableHeader>
          <TableBody>
            {table.getRowModel().rows.map((row) => (
              <TableRow key={row.id}>
                {row.getVisibleCells().map((cell) => (
                  <TableCell key={cell.id}>
                    {flexRender(cell.column.columnDef.cell, cell.getContext())}
                  </TableCell>
                ))}
              </TableRow>
            ))}
          </TableBody>
        </Table>
      </div>
    </div>
  )
}

// ============================================
// Multi-Step Form Wizard — FIXED with useFormContext
// ============================================

'use client'

import { useState } from 'react'
import { useForm, FormProvider, useFormContext } from 'react-hook-form'
import { zodResolver } from '@hookform/resolvers/zod'
import { z } from 'zod'
import { Button } from '@/components/ui/button'
import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card'
import { Input } from '@/components/ui/input'
import { Label } from '@/components/ui/label'
import { cn } from '@/lib/utils'
import { Check } from 'lucide-react'

// Per-step schemas
const step1Schema = z.object({ firstName: z.string().min(1, 'First name is required'), lastName: z.string().min(1, 'Last name is required'), email: z.string().email('Valid email is required') })
const step2Schema = z.object({ company: z.string().min(1, 'Company is required'), role: z.string().min(1, 'Role is required'), teamSize: z.string().min(1, 'Team size is required') })
const step3Schema = z.object({ plan: z.enum(['starter', 'pro', 'enterprise']), billingCycle: z.enum(['monthly', 'annual']) })

const fullSchema = step1Schema.merge(step2Schema).merge(step3Schema)

type FormData = z.infer<typeof fullSchema>

const steps = [
  { label: 'Personal', schema: step1Schema },
  { label: 'Organization', schema: step2Schema },
  { label: 'Plan', schema: step3Schema },
  { label: 'Review', schema: z.object({}) }
]

function StepPersonal() {
  const { register, formState: { errors } } = useFormContext<FormData>()
  return (
    <div className="space-y-4">
      <div className="grid grid-cols-2 gap-4">
        <div className="space-y-2">
          <Label htmlFor="firstName">First name</Label>
          <Input id="firstName" {...register('firstName')} />
          {errors.firstName && <p className="text-sm text-destructive">{errors.firstName.message}</p>}
        </div>
        <div className="space-y-2">
          <Label htmlFor="lastName">Last name</Label>
          <Input id="lastName" {...register('lastName')} />
          {errors.lastName && <p className="text-sm text-destructive">{errors.lastName.message}</p>}
        </div>
      </div>
      <div className="space-y-2">
        <Label htmlFor="email">Email</Label>
        <Input id="email" type="email" {...register('email')} />
        {errors.email && <p className="text-sm text-destructive">{errors.email.message}</p>}
      </div>
    </div>
  )
}

// StepOrganization, StepPlan, and StepReview follow the same pattern with useFormContext + error display (omitted for brevity but identical structure)

function StepReview({ data }: { data: FormData }) {
  return (
    <div className="space-y-4">
      <h3 className="text-lg font-semibold">Review your information</h3>
      <dl className="grid grid-cols-2 gap-2 text-sm">
        <dt className="text-muted-foreground">Name</dt><dd>{data.firstName} {data.lastName}</dd>
        <dt className="text-muted-foreground">Email</dt><dd>{data.email}</dd>
        <dt className="text-muted-foreground">Company</dt><dd>{data.company}</dd>
        <dt className="text-muted-foreground">Plan</dt><dd>{data.plan} ({data.billingCycle})</dd>
      </dl>
    </div>
  )
}

export function OnboardingWizard() {
  const [step, setStep] = useState(0)
  const methods = useForm<FormData>({
    resolver: zodResolver(fullSchema),
    defaultValues: { firstName: '', lastName: '', email: '', company: '', role: '', teamSize: '', plan: 'starter', billingCycle: 'monthly' }
  })
  const { handleSubmit, trigger, getValues } = methods

  const stepFields = { 0: ['firstName','lastName','email'] as const, 1: ['company','role','teamSize'] as const, 2: ['plan','billingCycle'] as const } as const

  async function nextStep() {
    const isValid = await trigger(stepFields[step as keyof typeof stepFields])
    if (isValid) setStep((s) => Math.min(s + 1, steps.length - 1))
  }

  function prevStep() { setStep((s) => Math.max(s - 1, 0)) }

  const onSubmit = async (data: FormData) => { console.log('Submitting:', data) }

  return (
    <FormProvider {...methods}>
      <Card className="mx-auto max-w-lg">
        <CardHeader>
          <CardTitle>Get started</CardTitle>
          <StepIndicator current={step} total={steps.length} />
        </CardHeader>
        <CardContent>
          <div aria-live="polite" className="sr-only">Step {step + 1} of {steps.length}: {steps[step].label}</div>
          <form onSubmit={handleSubmit(onSubmit)}>
            {step === 0 && <StepPersonal />}
            {step === 1 && <StepOrganization />}
            {step === 2 && <StepPlan />}
            {step === 3 && <StepReview data={getValues()} />}
            <div className="mt-6 flex justify-between">
              <Button type="button" variant="outline" onClick={prevStep} disabled={step === 0}>Back</Button>
              {step < steps.length - 1 ? (
                <Button type="button" onClick={nextStep}>Continue</Button>
              ) : (
                <Button type="submit">Submit</Button>
              )}
            </div>
          </form>
        </CardContent>
      </Card>
    </FormProvider>
  )
}

// ============================================
// Analytics Dashboard Cards — v0 scaffold + data layer
// ============================================

'use client'

import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card'
import { Skeleton } from '@/components/ui/skeleton'
import { cn } from '@/lib/utils'
import { TrendingUp, TrendingDown, Users, DollarSign, ShoppingCart, Activity } from 'lucide-react'

interface MetricCard {
  title: string
  value: string | number
  change: number
  changeLabel: string
  icon: React.ComponentType<{ className?: string }>
}

interface DashboardCardsProps {
  metrics: MetricCard[]
  isLoading: boolean
}

function MetricCard({ metric }: { metric: MetricCard }) {
  const isPositive = metric.change >= 0
  const TrendIcon = isPositive ? TrendingUp : TrendingDown
  return (
    <Card>
      <CardHeader className="flex flex-row items-center justify-between pb-2">
        <CardTitle className="text-sm font-medium text-muted-foreground">{metric.title}</CardTitle>
        <metric.icon className="h-4 w-4 text-muted-foreground" />
      </CardHeader>
      <CardContent>
        <div className="text-2xl font-bold">{metric.value}</div>
        <p className="mt-1 flex items-center gap-1 text-xs">
          <TrendIcon className={cn('h-3 w-3', isPositive ? 'text-emerald-600' : 'text-red-600')} />
          <span className={cn(isPositive ? 'text-emerald-600' : 'text-red-600')}>{isPositive ? '+' : ''}{metric.change}%</span>
          <span className="text-muted-foreground">{metric.changeLabel}</span>
        </p>
      </CardContent>
    </Card>
  )
}

function MetricCardSkeleton() {
  return (
    <Card>
      <CardHeader className="flex flex-row items-center justify-between pb-2">
        <Skeleton className="h-4 w-24" />
        <Skeleton className="h-4 w-4" />
      </CardHeader>
      <CardContent>
        <Skeleton className="h-8 w-32" />
        <Skeleton className="mt-2 h-3 w-20" />
      </CardContent>
    </Card>
  )
}

export function DashboardCards({ metrics, isLoading }: DashboardCardsProps) {
  if (isLoading) {
    return (
      <div className="grid gap-4 sm:grid-cols-2 lg:grid-cols-4">
        {Array.from({ length: 4 }).map((_, i) => <MetricCardSkeleton key={i} />)}
      </div>
    )
  }
  return (
    <div className="grid gap-4 sm:grid-cols-2 lg:grid-cols-4">
      {metrics.map((metric) => <MetricCard key={metric.title} metric={metric} />)}
    </div>
  )
}

// ============================================
// Command Palette — v0 scaffold + cmdk integration
// ============================================

'use client'

import { useEffect, useState } from 'react'
import { Command, CommandDialog, CommandEmpty, CommandGroup, CommandInput, CommandItem, CommandList, CommandSeparator } from '@/components/ui/command'
import { useRouter } from 'next/navigation'
import { File, Search, Settings, Users, LayoutDashboard, CreditCard } from 'lucide-react'

interface CommandAction {
  id: string
  label: string
  icon: React.ComponentType<{ className?: string }>
  action: () => void
  category: string
  keywords?: string[]
}

const RECENT_KEY = 'command-palette-recent'

function getRecentCommands(): string[] {
  if (typeof window === 'undefined') return []
  try { return JSON.parse(localStorage.getItem(RECENT_KEY) ?? '[]') } catch { return [] }
}

function addRecentCommand(id: string) {
  const recent = getRecentCommands().filter((r) => r !== id)
  recent.unshift(id)
  localStorage.setItem(RECENT_KEY, JSON.stringify(recent.slice(0, 5)))
}

export function CommandPalette() {
  const [open, setOpen] = useState(false)
  const router = useRouter()

  useEffect(() => {
    function handleKeyDown(e: KeyboardEvent) {
      if (e.key === 'k' && (e.metaKey || e.ctrlKey)) { e.preventDefault(); setOpen((prev) => !prev) }
    }
    document.addEventListener('keydown', handleKeyDown)
    return () => document.removeEventListener('keydown', handleKeyDown)
  }, [])

  const commands: CommandAction[] = [ /* same as previous version */ ]

  function runCommand(command: CommandAction) {
    addRecentCommand(command.id)
    command.action()
    setOpen(false)
  }

  const recentIds = getRecentCommands()
  const recentCommands = commands.filter((c) => recentIds.includes(c.id))

  return (
    <CommandDialog open={open} onOpenChange={setOpen}>
      <CommandInput placeholder="Type a command or search..." />
      <CommandList>
        <CommandEmpty>No results found.</CommandEmpty>
        {recentCommands.length > 0 && (
          <CommandGroup heading="Recent">
            {recentCommands.map((command) => (
              <CommandItem key={command.id} onSelect={() => runCommand(command)}>
                <command.icon className="mr-2 h-4 w-4" />{command.label}
              </CommandItem>
            ))}
          </CommandGroup>
        )}
        {['Navigation', 'Actions'].map((category) => {
          const groupCommands = commands.filter((c) => c.category === category)
          return (
            <CommandGroup key={category} heading={category}>
              {groupCommands.map((command) => (
                <CommandItem key={command.id} keywords={command.keywords} onSelect={() => runCommand(command)}>
                  <command.icon className="mr-2 h-4 w-4" />{command.label}
                </CommandItem>
              ))}
            </CommandGroup>
          )
        })}
      </CommandList>
    </CommandDialog>
  )
}

// ============================================
// Notification Toast System — v0 scaffold + sonner
// ============================================

// Provider in app/layout.tsx
import { Toaster } from '@/components/ui/sonner'
// <Toaster position="top-right" richColors closeButton />

// Toast utility in lib/toast.ts
import { toast } from 'sonner'

export const notify = {
  success({ title, description, action, duration = 4000 }: ToastOptions) {
    toast.success(title, { description, duration, action: action ? { label: action.label, onClick: action.onClick } : undefined })
  },
  error({ title, description, action, duration = 6000 }: ToastOptions) {
    toast.error(title, { description, duration, action: action ? { label: action.label, onClick: action.onClick } : undefined })
  },
  // warning, info, promise methods unchanged
}

// Usage example (in any component)
// notify.success({ title: 'Invoice sent', description: 'The invoice was emailed to the customer.', action: { label: 'Undo', onClick: () => undoSend() } })
// notify.promise(saveInvoice(data), { loading: 'Saving invoice...', success: 'Invoice saved successfully', error: (err) => `Failed to save: ${err.message}` })

// io.thecodeforge — javascript tutorial

// globals.css — your single source of truth
:root {
  --background: 0 0% 100%;
  --foreground: 222.2 84% 4.9%;
  --primary: 222.2 47.4% 11.2%;
  --primary-foreground: 210 40% 98%;
  --muted: 210 40% 96.1%;
  --border: 214.3 31.8% 91.4%;
}

.dark {
  --background: 222.2 84% 4.9%;
  --foreground: 210 40% 98%;
  --primary: 210 40% 98%;
  --primary-foreground: 222.2 47.4% 11.2%;
}

// Tailwind config — map them to utilities
module.exports = {
  theme: {
    extend: {
      colors: {
        primary: 'hsl(var(--primary))',
        muted: 'hsl(var(--muted))',
        border: 'hsl(var(--border))',
      }
    }
  }
}

// io.thecodeforge — javascript tutorial

import React from 'react';
import { Card, CardHeader, CardTitle, CardDescription, CardFooter } from '@/components/ui/card';
import { Button } from '@/components/ui/button';

class ErrorBoundary extends React.Component {
  constructor(props) {
    super(props);
    this.state = { hasError: false, error: null };
  }

  static getDerivedStateFromError(error) {
    return { hasError: true, error };
  }

  componentDidCatch(error, info) {
    console.error('Render crash:', error, info);
    // Push to your observability tool here — don't swallow it
  }

  render() {
    if (this.state.hasError) {
      return (
        <Card className="mx-auto mt-8 max-w-md">
          <CardHeader>
            <CardTitle>Something broke</CardTitle>
            <CardDescription>
              The component hit an unexpected state.
            </CardDescription>
          </CardHeader>
          <CardFooter>
            <Button onClick={() => this.setState({ hasError: false })}>
              Retry
            </Button>
          </CardFooter>
        </Card>
      );
    }
    return this.props.children;
  }
}

export default ErrorBoundary;

// io.thecodeforge — javascript tutorial

// event-bus.js — one singleton to rule them all
const listeners = {};

export const EventBus = {
  publish(event, data) {
    if (!listeners[event]) return;
    listeners[event].forEach(cb => cb(data));
  },
  subscribe(event, callback) {
    if (!listeners[event]) {
      listeners[event] = [];
    }
    listeners[event].push(callback);
    // return unsubscribe function
    return () => {
      listeners[event] = listeners[event].filter(cb => cb !== callback);
    };
  }
};

// Usage in CommandPalette
import { EventBus } from './event-bus';
// ... when command executed
EventBus.publish('settings:changed', { key: 'theme', value: 'dark' });

// Usage in ToastSystem
import { EventBus } from './event-bus';
useEffect(() => {
  const unsub = EventBus.subscribe('settings:changed', (payload) => {
    toast({ title: `${payload.key} updated to ${payload.value}` });
  });
  return () => unsub();
}, []);